Laboratory culture of larvae of several species of echinoderms at Friday Harbor Laboratories, Washington, including sea cucumbers Parastichopus californicus, indicate a common pattern of suspension feeding.  The studies involve videotaping larvae as they capture 20µm diameter plastic spheres, while simultaneously recording elapsed time and later measuring lengths of ciliated bands, arms, and other features.  The drawing shows a Parastichopus auricularia larva of 1.2mm in length capturing a single plastic microsphere over a time span of 2.7sec. Note that the sphere is first captured on one of the ciliary bands to the right of the mouth and then a second time on a band just posterior to the mouth.  The particle then is moved toward the larval midline and into the mouth.  Interestingly, few particles, even these plastic ones, are lost after capture.  The author records only 29 incidences of loss out of 443 captures (6%).  Hart 1991 Biol Bull 180: 12; see Paltzat et al. 2008 Aquaculture 275: 124 for an account of joint culture of sea cucumbers P. californicus with Pacific oysters Crassostrea gigas.

NOTE the ciliated band of the larva is shown by the dark lines

Depending upon species, adult sea cucumbers feed either by catching organic food particles suspended in the water column or by collecting detritus from the sea bottom.  Both methods involve the capture of food on tentacles arising from around the mouth.  In Parastichopus californicus, each of 5 major tentacles branch several times to make 5 mop-like structures with multiple adhesive pads or nodules.  When these are splayed against the substratum, food matter adheres, primarily through attachment to sticky mucus secreted by the skin, and secondarily through physical entrapment among the tentacle nodules.  The tubular rod-shapes of the tentacle nodules are maintained by calcareous inclusions, the dermal spicules (ossicles). The tentacles are periodically inserted into the pharynx where they are wiped clean against the pharyngeal wall.  Cameron & Fankboner 1984 J Exp Mar Biol Ecol 81: 193.

Anterior end of Parastichopus californicus with tentacles
withdrawn and mouth facing away from the viewer 1X

Parastichopus californicus feeds as it crawls slowly along.  Distance traveled is about 4m per day in summer.  daSilva et al. 1986 Mar Behav Physiol 12: 133.

Anus and rectum of P. californicus. The rectum doubles as a gas-exchange organ.
It is heavily muscled and rhythmic volume changes, combined with opening and
closing the anus, move water in and
out of large respiratory trees that
originate on the rectum's inner surface 2X

Parastichopus californicus with characteristic ropey feces. The anus of one
individual is partly open. Fecal production in Parastichopus is continuous 0.7X

Psolus chitonoides is a suspension-feeder, and the mechanism of particle collection is similar to that described in Research Study 2 for Parastichopus. Psolus catches organic particles in sticky mucus secreted by papillae on its tentacles or physically ensnares them in the papillae.  At rest, the papillae are withdrawn fully or partially (as shown on the Right); when feeding, they are extended as fine branchlets to expose more surface area (see photo in Research Study 5 below).  The tentacles are periodically inserted into the pharynx and cleaned of their load of particles.  Inorganic matter eaten along with organic material is passed through the gut to emerge with the feces from the anus.  Fankboner 1978 J Exp Mar Biol Ecol 31: 11.

Black sea cucumbers  Cucumaria pseudocurata in Sonoma County, California grow to adult size within a year of hatching.  This is a brooding species and, although documentation is needed, dispersal may be mainly by water movement. Aggregations on intertidal rock-wall habitats can be quite dense, a feature that may minimise desiccation during low-tide periods.

Survival after the first year of life is negatively correlated with density, at least on wall habitats (see graph on Right).  However, the author notes that individuals that go missing may not necessarily die.  Some may re-attach in another habitat, and this gives rise to the idea that water movements may be involved in dispersal.  Adults live to about 5yr of age.  Rutherford 1973 Mar Biol 22: 167.

NOTE  this species also lives amongst sea mussels and survival likely varies between habitats

NOTE survival is monitored in 16 cm² quadrats located at +0.3m tide level

The sea cucumber Leptosynapta clarki lives on intertidal mudflats along the Pacific coast from the islands of Haida Gwai, British Columbia to central California.  Studies at the Bamfield Marine Sciences Centre, British Columbia show that juveniles of 1-2mm in length are released from the brooding female parent via ruptures in the body wall in springtime, after which they immediately burrow into the sediment.  By August of the same year they reach a size of about 16mm and, by the commencement of reproductive period in November, are about 35mm in length and are reproductively active as males.  By 1yr of age they have reached a mean size of about 20mm.  Sewell 1994 Mar Ecol Progr Ser 114: 149.

NOTE  Leptosynapta clarki is a protandrous hermaphrodite

Investigation of field growth in sea cucumbers, as in other animals, may require that individuals be tagged to identify them over time. To this end, researchers at the National Marine Fisheries Service, Alaska monitor retention rates of 6 types of tags¹ by sea cucumbers Parastichopus californicus² and assess post-tagging/handling effects on locomotory behaviour.  In laboratory trials, the single T-bar tag is found to have highest retention rate: 70% after 16wk and 40% after 32wk.  In field trials within naturally delimited plots, individuals tagged twice with modified T-bar FD-94 tags and ones “handled but not tagged³” move significantly further than “non-tagged” controls over 24h (see histogram).  On the strength of their results, the authors recommend that researchers minimise handling and wait at least 24h after tagging before using the tagged individuals in studies of behaviour.  The reader still wonders, though, whether it is the effect of  the tagging procedure, general handling, or the presence of the tag itself (T-bar tags apparently produce sores and lesions that may not be visible for several weeks) that leads to the increased locomotory activity.  The treatments are not clearly separated in the study.  These might repay further investigation, as would continued monitoring past the arbitrary 24h period set by the researchers.  Is it possible that the continued waggling stimulation of a T-bar tag in the epithelium or prolonged infection could lead to longer-term stimulation?  Cieciel et al. 2009 NA J Fisheries Management 29: 288.

NOTE¹  these include Floy banner FTSL-73, cinch FT-4C, fingerling FTF-69, garment, single T-bar FD-94, and coded wire tags

NOTE²  the species supports small fisheries in all west-coast regions save for Oregon.  The flesh is used in different forms (pickled, dried, powdered) as a garnish in many dishes, and in stir-fry and soup preparations in many Asian countries

NOTE³  the researchers note that in order to monitor the “handled” and “control” groups in the field plots that would otherwise be visually inseparable, individuals that had actually been tagged one month previously, and presumably with the tags still retained, are used instead of individuals previously untreated.  The reader should bear this in mind when considering the results